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|
/* Generate assembler source containing symbol information
*
* Copyright 2002 by Kai Germaschewski
*
* This software may be used and distributed according to the terms
* of the GNU General Public License, incorporated herein by reference.
*
* Usage: nm -n vmlinux | scripts/kallsyms [--all-symbols] > symbols.S
*
* Table compression uses all the unused char codes on the symbols and
* maps these to the most used substrings (tokens). For instance, it might
* map char code 0xF7 to represent "write_" and then in every symbol where
* "write_" appears it can be replaced by 0xF7, saving 5 bytes.
* The used codes themselves are also placed in the table so that the
* decompresion can work without "special cases".
* Applied to kernel symbols, this usually produces a compression ratio
* of about 50%.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define KSYM_NAME_LEN 128
struct sym_entry {
unsigned long long addr;
unsigned int len;
unsigned int start_pos;
unsigned char *sym;
};
static struct sym_entry *table;
static unsigned int table_size, table_cnt;
static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
static int all_symbols = 0;
static char symbol_prefix_char = '\0';
int token_profit[0x10000];
/* the table that holds the result of the compression */
unsigned char best_table[256][2];
unsigned char best_table_len[256];
static void usage(void)
{
fprintf(stderr, "Usage: kallsyms [--all-symbols] [--symbol-prefix=<prefix char>] < in.map > out.S\n");
exit(1);
}
/*
* This ignores the intensely annoying "mapping symbols" found
* in ARM ELF files: $a, $t and $d.
*/
static inline int is_arm_mapping_symbol(const char *str)
{
return str[0] == '$' && strchr("atd", str[1])
&& (str[2] == '\0' || str[2] == '.');
}
static int read_symbol(FILE *in, struct sym_entry *s)
{
char str[500];
char *sym, stype;
int rc;
rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, str);
if (rc != 3) {
if (rc != EOF) {
/* skip line */
fgets(str, 500, in);
}
return -1;
}
sym = str;
/* skip prefix char */
if (symbol_prefix_char && str[0] == symbol_prefix_char)
sym++;
/* Ignore most absolute/undefined (?) symbols. */
if (strcmp(sym, "_text") == 0)
_text = s->addr;
else if (strcmp(sym, "_stext") == 0)
_stext = s->addr;
else if (strcmp(sym, "_etext") == 0)
_etext = s->addr;
else if (strcmp(sym, "_sinittext") == 0)
_sinittext = s->addr;
else if (strcmp(sym, "_einittext") == 0)
_einittext = s->addr;
else if (toupper(stype) == 'A')
{
/* Keep these useful absolute symbols */
if (strcmp(sym, "__kernel_syscall_via_break") &&
strcmp(sym, "__kernel_syscall_via_epc") &&
strcmp(sym, "__kernel_sigtramp") &&
strcmp(sym, "__gp"))
return -1;
}
else if (toupper(stype) == 'U' ||
is_arm_mapping_symbol(sym))
return -1;
/* exclude also MIPS ELF local symbols ($L123 instead of .L123) */
else if (str[0] == '$')
return -1;
/* exclude debugging symbols */
else if (stype == 'N')
return -1;
/* include the type field in the symbol name, so that it gets
* compressed together */
s->len = strlen(str) + 1;
s->sym = malloc(s->len + 1);
if (!s->sym) {
fprintf(stderr, "kallsyms failure: "
"unable to allocate required amount of memory\n");
exit(EXIT_FAILURE);
}
strcpy((char *)s->sym + 1, str);
s->sym[0] = stype;
return 0;
}
static int symbol_valid(struct sym_entry *s)
{
/* Symbols which vary between passes. Passes 1 and 2 must have
* identical symbol lists.
*/
static char *special_symbols[] = {
/* Exclude linker generated symbols which vary between passes */
"_SDA_BASE_", /* ppc */
"_SDA2_BASE_", /* ppc */
NULL };
int i;
int offset = 1;
/* skip prefix char */
if (symbol_prefix_char && *(s->sym + 1) == symbol_prefix_char)
offset++;
/* if --all-symbols is not specified, then symbols outside the text
* and inittext sections are discarded */
if (!all_symbols) {
if ((s->addr < _stext || s->addr > _etext)
&& (s->addr < _sinittext || s->addr > _einittext))
return 0;
/* Corner case. Discard any symbols with the same value as
* _etext _einittext; they can move between pass 1 and 2 when
* the kallsyms data are added. If these symbols move then
* they may get dropped in pass 2, which breaks the kallsyms
* rules.
*/
if ((s->addr == _etext &&
strcmp((char *)s->sym + offset, "_etext")) ||
(s->addr == _einittext &&
strcmp((char *)s->sym + offset, "_einittext")))
return 0;
}
/* Exclude symbols which vary between passes. */
if (strstr((char *)s->sym + offset, "_compiled.") ||
strncmp((char*)s->sym + offset, "__compound_literal.", 19) == 0 ||
strncmp((char*)s->sym + offset, "__compound_literal$", 19) == 0)
return 0;
for (i = 0; special_symbols[i]; i++)
if( strcmp((char *)s->sym + offset, special_symbols[i]) == 0 )
return 0;
return 1;
}
static void read_map(FILE *in)
{
while (!feof(in)) {
if (table_cnt >= table_size) {
table_size += 10000;
table = realloc(table, sizeof(*table) * table_size);
if (!table) {
fprintf(stderr, "out of memory\n");
exit (1);
}
}
if (read_symbol(in, &table[table_cnt]) == 0) {
table[table_cnt].start_pos = table_cnt;
table_cnt++;
}
}
}
static void output_label(char *label)
{
if (symbol_prefix_char)
printf(".globl %c%s\n", symbol_prefix_char, label);
else
printf(".globl %s\n", label);
printf("\tALGN\n");
if (symbol_prefix_char)
printf("%c%s:\n", symbol_prefix_char, label);
else
printf("%s:\n", label);
}
/* uncompress a compressed symbol. When this function is called, the best table
* might still be compressed itself, so the function needs to be recursive */
static int expand_symbol(unsigned char *data, int len, char *
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